If you want a patch to be considered for inclusion in Xapian, you
must own the copyright on your changes. Employers often claim copyright on code
written by their employees (even if the code is written in their spare time),
so please check with your employer if this applies. Be aware that even if you
are a student your university may try and claim some rights on code which you
write.

Patches which are submitted to Xapian will only be included if the
copyright holder(s) dual-license them under each of the following
licences:

GPL version 2 and all later versions (see the file COPYING
in xapian-core for details).

MIT/X license:

Copyright (c) <year> <copyright holders>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to
deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.

The current distribution of Xapian contains many files which are only licensed
under the GPL, but we are working towards being able to distribute Xapian under
a more permissive license, and are not willing to accept patches which we will
have to rewrite before this can happen.